Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$52.59	4.485%	$54.9487	$54.95	$54.95	$54.90
Purchase #2	$26.29	4.692%	$27.5235	$27.52	$27.50	$27.50
Purchase #3	$228.49	8.256%	$247.3541	$247.35	$247.35	$247.40
Purchase #4	$74.72	9.205%	$81.598	$81.60	$81.60	$81.60
Purchase #5	$94.91	6.739%	$101.306	$101.31	$101.30	$101.30
Purchase #6	$84.39	5.549%	$89.0728	$89.07	$89.05	$89.10
Purchase #7	$5.53	6.473%	$5.888	$5.89	$5.90	$5.90
7 purchase totals =	$566.92		$607.6911	$607.69	$607.65	$607.70